The present invention relates to an ultrasonic hand piece to be used for cutting a bone in the living body operation and an ultrasonic horn for use with the same.
In the medical treatment field, a number of ultrasonic hand pieces have been used as one of the variety of operation instruments in the surgical field.
FIG. 9 is a drawing showing an ultrasonic hand piece A to be used specifically for cutting a bone among such ultrasonic hand pieces.
In the figure, 1 denotes a casing for accommodating an ultrasonic vibration mechanism which is equipped with a vibrator of magnetostriction type, electrostriction type, or other type, and outputs an ultrasonic wave at the specified frequency; 2 a horn which is inserted into an opening portion at one end of the casing for cutting a bone or other tissue 3 with its end portion by the vibration transmitted from said ultrasonic vibration mechanism; 1a a joint for a tube for sucking the irrigation fluid, the cut debris, and the like; 1b a joint for a tube for injecting the irrigation fluid to cool the friction heat generated in cutting the bone; and 1c a cable for supplying high-frequency electric energy to said ultrasonic vibration mechanism.
By the vibration transmitted from the ultrasonic vibration mechanism, the horn 2 is vibrated at the specified frequency in the axial direction, and with the tip contacting the bone or other tissue 3, cuts the required site.
FIG. 10 is a figure showing the cutting operation on a bone or other hard tissue with the horn in said ultrasonic hand piece A. At the tip of the horn 2, a hook-shaped scalpel portion 2a is formed, and the operator operates the ultrasonic hand piece A from the direction of view indicated with the arrow C to move the horn 2 in the direction of the arrow B, while carrying out the cutting of the required site of the bone or other hard tissue with the tip of the scalpel portion 2a which is reciprocated in the direction of the arrow A. In such cutting, the vibration from the tip of the scalpel portion 2a is transmitted to the portion P of the bone or other hard tissue H opposing to the tip for finely fracturing it as shown in FIG. 11, and then, the finely fractured portion is raked with the tip of the scalpel portion 2a. 
However, the tip of the scalpel portion 2a is finely vibrated at a rate of 25,000 cycles/sec with a stroke of 200 xcexcm, thus the speed of the tip is 50 km/h at maximum.
Therefore, stresses are concentrated into the contacting portion of the sharply formed tip, which often causes the tip of the scalpel portion 2a to deeply penetrate into the tissue inside. If the tip deeply cuts into the tissue inside in this way, the bone is cut in quantity at a time, which not only requires a large amount of ultrasonic vibrational energy, but also requires the operator to exert a large force for operating the scalpel portion. In addition, because the tip of the scalpel portion tends to sting into the bone, there occurs a problem of that precise control of the amount of cut is difficult.
With the above-mentioned prior art, the scalpel portion is protruded at right angles to the horn main body, thus, as shown in FIG. 10, it is inevitable that the horn is positioned approximately in parallel to the surface of the bone H in operation, and thus the operator has been forced to make operation in an extremely narrow field of view in the direction of the arrow C.
Further, the above-mentioned prior art has presented a problem of that, if the scalpel portion is contacted with a site where water is collected, the water is atomized by the vibration, which hinders the sight of the operator. In addition, when cutting the bone and fracturing and sucking the tumor produced around it are alternatively performed, it has been conventionally required to prepare a hand piece for bone cutting and that for tumor fracturing and sucking, and to use either of them as needed.
The present invention is intended to solve the above mentioned conventional problems by providing an ultrasonic hand piece comprising an ultrasonic vibration mechanism which outputs a longitudinal ultrasonic vibration, a twisted ultrasonic vibration, or a compounded longitudinal and twisted ultrasonic vibration, a casing for accommodating the ultrasonic vibration mechanism, and a horn which is mounted at one end of the casing for cutting a bone or other hard tissue by the vibration transmitted from said ultrasonic vibration mechanism,
wherein said horn comprises a main body portion and a scalpel portion which is formed at the tip of the main body portion for cutting a bone or other hard tissue, and in the end portion of the scalpel portion is formed a working portion which comprises at least one face portion for eliminating the stress concentration into the object site of a bone or other hard tissue to prevent excessive sting while transmitting a vibration for forming a finely fractured layer, and an edge portion for raking the bone tissue finely fractured by the working portion.
With the above-stated configuration, said scalpel portion may be formed in a hook-like shape so as to protrude from the main body portion side wall at the tip of the main body portion.
In addition, with the above-stated configuration, the angle of aperture for the hook-shaped scalpel with respect to the horn main body portion may be set in the range where the included angle between the internal side of the hook-shaped scalpel and the main body portion side wall is larger than a right angle and smaller than two right angles, so that a sufficient field of view for the operator can be secured between the cut portion and the main body portion.
Further, with the above-stated ultrasonic hand piece, an engaging portion to prevent sliding in contact with a bone or other hard tissue may be formed in the working portion at the tip of the scalpel portion.
In addition, with the above-stated ultrasonic hand piece, the outline portion of the hook-shaped scalpel portion may be formed in a curved shape in section, i.e., an approximately arc shape in section so that a receiving portion for cut bone tissue is formed between the main body portion and the scalpel portion for facilitating the cutting operation.
The present invention is also intended to solve the above mentioned conventional problems by constituting the ultrasonic horn for cutting a bone or other hard tissue by the vibration transmitted from an ultrasonic vibration source with a main body portion and a scalpel portion which is formed at the tip of the main body portion for cutting a bone or other hard tissue, and in the end portion of the scalpel portion, forming a working portion which comprises at least one face portion for eliminating the stress concentration into the object site of a bone or other hard tissue to prevent excessive sting while transmitting a vibration for forming a finely fractured layer, and an edge portion for raking the bone tissue finely fractured by the working portion.
With said ultrasonic horn, said scalpel portion may be formed in a hook-like shape so as to protrude from the main body portion side wall at the tip of the main body portion.
In addition, with the above-stated ultrasonic horn, the angle of aperture for the hook-shaped scalpel with respect to the horn main body portion may be set in the range where the included angle between the internal side of the hook-shaped scalpel and the main body portion side wall is larger than a right angle and smaller than two right angles, so that a sufficient field of view for the operator can be secured between the cut portion and the main body portion.
Further, with the above-stated ultrasonic horn, an engaging portion to prevent sliding in contact with a bone or other hard tissue may be formed in the working portion at the tip of the scalpel portion.
Still further, the outline portion of the hook-shaped scalpel portion may be formed in a curved shape in section, i.e., an approximately arc shape in section so that a receiving portion for cut bone tissue is formed between the main body portion and the scalpel portion.
And further, with the above-stated ultrasonic hand piece or ultrasonic horn, a suction passage is formed which, starting from one or more opening portions provided in the vicinity of the scalpel portion of the ultrasonic horn, runs through the horn main body portion to be connected to the suction mechanism, facilitating the suction and discharge of the water, the cut debris, the fracture debris, and the like in the operation site for allowing the proper and efficient operation.
With the present invention, the above-described configurations allow the following effects to be expected.
(1) The various problems which can be presented by the scalpel portion of an ultrasonic hand piece making an excessive sting into the cut site can be eliminated, and the movement of the scalpel portion can be precisely controlled, which allows precision cutting of a bone or other hard tissue to achieve the purpose of the medical treatment.
(2) The operator can always grasp the cutting situation in a wide field of view, which allows the operation to be made with safety and ease.